feat: monitor large process heaps and long message queues

lib/supavisor/erl_sys_mon.ex

@@ -4,19 +4,23 @@ defmodule Supavisor.ErlSysMon do
   """
 
   use GenServer
+  alias Supavisor.Helpers
 
   require Logger
 
   def start_link(args) do
-    GenServer.start_link(__MODULE__, args, name: __MODULE__)
+    name = args[:name] || __MODULE__
+    GenServer.start_link(__MODULE__, args, name: name)
   end
 
   def init(_args) do
     :erlang.system_monitor(self(), [
       :busy_dist_port,
       :busy_port,
       {:long_gc, 250},
-      {:long_schedule, 100}
+      {:long_schedule, 100},
+      {:long_message_queue, {0, 1_000}},
+      {:large_heap, Helpers.mb_to_words(25)}
     ])
 
     {:ok, []}

lib/supavisor/helpers.ex

@@ -378,4 +378,18 @@ defmodule Supavisor.Helpers do
   def validate_name(name) do
     byte_size(name) in 1..@max_length and String.printable?(name)
   end
+
+  @doc """
+  Converts megabytes to Erlang words.
+
+  ## Examples
+
+      iex> Supavisor.Helpers.mb_to_words(1)
+      131_072
+
+      iex> Supavisor.Helpers.mb_to_words(1.5)
+      196_608
+  """
+  @spec mb_to_words(number()) :: pos_integer()
+  def mb_to_words(mb), do: round(mb * 1_048_576 / :erlang.system_info(:wordsize))
 end

test/supavisor/erl_sys_mon_test.exs

@@ -0,0 +1,44 @@
+defmodule Supavisor.ErlSysMonTest do
+  use ExUnit.Case, async: false
+  import ExUnit.CaptureLog
+  alias Supavisor.ErlSysMon
+
+  test "starts and configures monitor with custom name" do
+    assert {:ok, pid} = ErlSysMon.start_link(name: __MODULE__)
+    assert Process.whereis(__MODULE__) == pid
+
+    {monitor_pid, settings} = :erlang.system_monitor()
+    assert monitor_pid == pid
+
+    [
+      :busy_dist_port,
+      :busy_port,
+      {:long_gc, 250},
+      {:long_schedule, 100},
+      {:long_message_queue, {0, 1_000}},
+      {:large_heap, 3_276_800}
+    ]
+    |> Enum.each(&assert &1 in settings)
+
+    test_msg = {:monitor, self(), :test_pid, :busy_port}
+
+    log =
+      capture_log(fn ->
+        send(pid, test_msg)
+        Process.sleep(100)
+      end)
+
+    assert log =~ "Supavisor.ErlSysMon message:"
+    assert log =~ inspect(test_msg)
+
+    Process.exit(pid, :normal)
+  end
+
+  test "starts with default name when no args provided" do
+    pid = Process.whereis(ErlSysMon)
+    assert is_pid(pid)
+    assert Process.alive?(pid)
+
+    assert {:error, {:already_started, ^pid}} = ErlSysMon.start_link([])
+  end
+end